Ablation of nerves is a common practice in the treatment of pain, and is currently used to treat back pain in the disc and in the facet joint. Ablation involves the heating of a tissue by the application of energy, in order to create a lesion; it is theorised that the lesioning of nerves renders them unable to transmit neural signals, thus eliminating nociceptive sensations therefrom. One common method of ablation involves the application of electrical energy from an electrode. Monopolar apparatuses use a grounding pad and a single electrode (or a group of electrodes at the same potential), whereby the electrical field is concentrated around the electrode(s) to generate heat within the tissue. Bipolar or multipolar apparatuses also exist, whereby the electrical current passes substantially between the electrodes, allowing a lesion to be created around each and, depending on the voltage or power used, extending between the electrodes.
Recently, research has led to growing interest in pain emanating from the sacroiliac (SI) joint and the surrounding region. Pain associated with the SI joint and surrounding region—which has been referred to in the literature as sacroiliac syndrome, sacroiliac joint dysfunction or sacroiliac joint complex (SIJC) pain amongst other terms—will, for clarity, be referred to throughout this specification as sacroiliac joint syndrome (SIJS). Referring to FIG. 1, the SI joint 110 is the region of a patient's body located between the sacrum 100, a large bone at the base of the spine composed of five fused vertebrae, and the ilium 102 of the pelvis. SI joint 110 is a relatively immobile joint, serving to absorb shock during locomotion. The structure of the SI joint varies significantly between individuals but generally comprises an articular cartilaginous surface, a ligamentous aspect and, in most cases, one or more synovial recesses. Historically, it was believed that SI pain was referred, and that the joint itself was not innervated, however, it has recently become accepted that nerves do enter the joint. Though the specific pathways of innervation have not yet been elucidated, the nerves responsible for SI pain are thought to comprise, at least in part, nerves 106 emanating from the sacral dorsal plexus, the network of nerves on the posterior surface of the sacrum, extending from the posterior primary rami or sacral nerves 108 that exit the sacral foramina 107. Diagnostic criteria for SIJS include (1) pain in the region of the SI joint with possible radiation to the groin, medial buttocks, and posterior thigh, (2) reproduction of pain by physical examination techniques that stress the joint, (3) elimination of pain with intra-articular injection of local anesthetic and (4) an ostensibly morphologically normal joint without demonstrable pathognomonic radiographic abnormalities.
While mechanical support devices exist for the alleviation of pain, there is currently no standardized method or apparatus for the treatment of SIJS. Yin et al. (Sensory Stimulation-Guided Sacroiliac Joint Radiofrequency Neurotonomy: Technique based on Neuroanatomy of the Dorsal Sacral Plexus; (2003) SPINE, Vol. 28, No. 20, pp. 2419-2425, which is incorporated herein by reference) suggest treatment of SIJS by lesioning a single branch of a sacral nerve as it exits the sacral foramina. The procedure described by Yin et al. may require a relatively skilled user due to the approach involved. In addition, the procedure detailed therein is time consuming as it involves multiple steps of probe re-positioning and neural stimulation in order to locate a single symptomatic nerve branch.